1. Field of the Invention
The present invention relates to a track rail mounting structure of a rectilinear guide apparatus, and more particularly, it relates to a track rail mounting structure of a rectilinear guide apparatus which can preferably be used in the case that a track rail and a base on which the track rail is mounted are made from materials having different thermal expansion coefficients.
2. Description of the Prior Art
FIG. 1 shows a constitution example of a rectilinear guide apparatus.
A rectilinear guide apparatus 1 of this type generally comprises a track rail 2 fixed to a fixing portion such as a head of a machining apparatus; and a slider 4 on which a movable member such as a table is mounted and which is engaged with the track rail 2 via a plenty of balls 3 as rotating/running members so as to perform rectilinear motion along the track rail 2.
The track rail 2 has a ball rotating/running groove 7 formed as a track where the balls 3 rotate and run, and on the other hand, the slider 4 has a ball rotating/running groove 8 formed as a load track opposing to the ball rotating/running groove 7 of the track rail 2, so that the balls 3 rotate and run between the ball rotating/running groove 7 and the ball rotating/running groove 8 while being subjected to a load.
Moreover, the slider 4 has a passage 6 formed for returning balls from one end to the other end of the ball rotating/running groove 8. This passage 6 and the aforementioned ball rotating/running groove 8 constitute an endless circulation route of the balls 3. The balls 3 circulate in this endless circulation route following the movement of the slider 4. Thus, the aforementioned slider 4 smoothly moves along the track rail 2.
When fixing to a base the track rail 2 of the rectilinear guide apparatus 1 having the aforementioned constitution, as shown in FIG. 2, a reference plane 10a is provided on the base 10, and one side surface of the track rail 2 is brought into abutment with the reference plane 10a, which is fixed to the upper surface of the base 10 with a bolt 20. Moreover, the other side surface of the track rail 2 is brought into abutment with a reinforcing member 21, which is fixed with a bolt 22.
However, as described above, when the track rail 2 is fixed to the base 10 with the bolt 20 (or a fixing member), in case the track rail 2 is made from a material having a thermal expansion coefficient different from that of a material constituting the base 10 (for example, the track rail 2 is made from iron and the base 10 is made from aluminum), a difference is caused in thermal expansion between the track rail 2 and the base 10 by a temperature change, which in turn causes distortion in the track rail 2.
Especially when arranging a plurality of rectilinear guide apparatuses 1 in parallel to one another on the base 10 and mounting a common table on their sliders 4, there is a problem that the table plane is displaced. This problem becomes especially remarkable when the rectilinear guide apparatus is used in an environment of a great temperature change.
It is therefore an object of the present invention to provide a track rail mounting structure of a rectilinear guide apparatus capable of absorbing an expansion difference between a track rail and a base caused by thermal expansion, so as not to distort the track rail by a temperature change even when the track rail of the rectilinear guide apparatus is made from a material having a thermal expansion coefficient different from that of a material constituting the base on which the track rail is mounted.
In order to achieve the aforementioned object, a track rail mounting structure of a rectilinear guide apparatus comprises a track rail having a rotating/running surface where a plenty of rotating/running bodies rotate and run; an endless circulation route for guiding the plenty of rotating/running bodies; and a slider movably arranged with respect to the track rail via the rotating/running bodies; wherein a base where the track rail is mounted has a groove for inserting a bottom portion of the track rail, so that the bottom portion of the track rail is inserted into the groove, and a pressure member is provided for pressing at least one side surface of the track rail toward an inner side surface of the groove.
As has been described above, since the pressure member is provided to press the side surface of the track rail toward the inner side surface of the groove, the side surface of the track rail is pressed by the pressure member so as to press the opposite side of the track rail to the inner side surface of the groove or both side surfaces of the track rail are pressed by the pressure member so as to be fixed to the track rail. Accordingly, even when a thermal expansion difference is caused between the track rail and the base by a temperature change, a contact portion of the pressure member slides along the side surface of the track rail so as to absorb the thermal expansion difference and accordingly, no distortion is caused in the track rail.
Moreover, the track rail mounting structure of the rectilinear guide apparatus is characterized in that the pressure member has a convex contact surface which is brought into abutment with the track rail side surface.
As has been described above, since the contact surface of the pressure member which is brought into abutment with the track rail side surface has a convex shape, the contact between the track rail side surface and the convex surface is a point-to-point contact or a linear contact. Even when a thermal expansion difference is caused between the track rail and the base by a temperature change, the convex contact portion slides along the side surface of the track rail so as to absorb the thermal expansion difference and accordingly, no distortion is caused in the track rail.
Moreover, the track rail mounting structure of the rectilinear guide apparatus is characterized in that the pressure member is an elastic corrugated spacer inserted between the side surface of the track rail and the inner side surface of the groove.
As has been described above, since the pressure member is the elastic corrugated spacer inserted between the side surface of the track rail and the inner side surface of the groove, a contact portion between the side surface of the track rail and the corrugated spacer is a linear contact. Even when a thermal expansion difference is caused between the track rail and the base, the contact portion of the corrugated spacer slides along the side surface of the track rail so as to absorb the thermal expansion difference and accordingly, no distortion is caused in the track rail.
Moreover, the track rail mounting structure of the rectilinear guide apparatus is characterized in that the pressure member is a spherical body which is inserted with pressure into a plurality of holes opened at a predetermined interval on the inner side surface of one side of the groove, so that the spherical body presses the side surface of the track rail.
As has been described above, the pressure member is a spherical body and a contact between the side surface of one side of the track rail and the spherical body is a point-to-point contact. Even when a thermal expansion difference is caused between the track rail and the base, the contact portion of the spherical body slides along the side surface of one side of the track rail so as to absorb the thermal expansion difference and accordingly, no distortion is caused in the track rail.
Moreover, the track rail mounting structure of the rectilinear guide apparatus is characterized in that a pressing force of the spherical body is reinforced by a pressing force reinforcing member inserted into the hole where the spherical body is inserted with pressure.
As has been described above, by inserting the pressing force reinforcing member with pressure into the hole where the spherical body is inserted with pressure, the pressing force of the spherical body is reinforced by the pressure member and the track rail is fixed firmly. Simultaneously with this, even when a thermal expansion difference is caused between the track rail and the base, a contact portion of the spherical body slides along the side surface of one side of the track rail so as to absorb the thermal expansion difference and accordingly, no distortion is caused in the track rail.
Moreover, the track rail mounting structure of the rectilinear guide apparatus is characterized in that the pressure member is a spherical body which is held by a holding metal member, and the metal member holding the spherical body is inserted with pressure into a plurality of holes opened at a predetermined interval on the inner side surface of the groove, so that the spherical body presses the side surface of the track rail.
As has been described above, in case the metal member holding the spherical body is inserted with pressure into a plurality of holes opened at a predetermined interval on the inner side surface of one side of the groove, so that the spherical body presses the side surface of one side of the track rail, similarly as the aforementioned, the side surface of one side of the track rail is in contact with the spherical body as a point-to-point contact. Even when a thermal expansion difference is caused between the track rail and the base, the contact portion of the spherical body slides along the side surface of one side of the track rail so as to absorb the thermal expansion difference and accordingly, no distortion is caused in the track rail.